Boy assaulted by man who climbed in window

A five-year-old boy has been indecently assaulted by a man who climbed in his bedroom window in Sydney's west.

The man entered the house on McMurdo Avenue, Tregear, about 3.20am (AEDT) on Sunday.

He then indecently assaulted the boy before leaving the home through the same window, police said.

Officers and other emergency services have established a crime scene, which has been examined by forensic specialists.

The boy was taken to Westmead Children's Hospital for medical examination.

Police are urging anyone with information or who saw anyone acting suspicious in the vicinity of McMurdo Avenue in the early hours of the morning to contact Mount Druitt Police Station or Crime Stoppers on 1800 333 000.